From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Design considerations for the Apache engine, including tappet adjustment, connecting rods, and bearings.
| Identifier | ExFiles\Box 4\1\ 01-page013 | |
| Date | 16th May 1938 | |
| V+04 To R.{Sir Henry Royce} From Hs.{Lord Ernest Hives - Chair} Hs.{Lord Ernest Hives - Chair}1/HJ.16.5.38. c. to H-S. c. to Wor.{Arthur Wormald - General Works Manager} c. to Hy.{Tom Haldenby - Plant Engineer} c. to RBD. APACHE ENGINE. Replying to R.2/HP.9.5.38. We are quite in agreement that some form of automatic adjustment will be essential on the 12 cyl. engine, where we shall have 24 tappets to adjust. As regards connecting rods, the recent work on Kestrel engines with Lead Bronze bearings has put an entirely different value on these compared with results obtained twelve months ago. Our curved root forked rod has proved itself to be a wonderful big end bearing construction. We think the results obtained might justify considering whether the size could be got down sufficiently to enable this form of rod to be used. We shall not have the same problem with the crankshaft of keeping clear of the master period and therefore it is probable that the shaft diameter could be reduced with no disadvantage. The chief advantage we can see in the forked rod over the side by side rod is that it should enable the engine to be made lighter and shorter. With regard to the third point the double/rear main bearing as at present used has given us no immunity from flywheel period. It does not appear to have decreased the tendency for the timing gears to rattle, and has made them very much less accessible. Furthermore the timing case in front has proved to be of material assistance in cooling the oil. As a proof of this, neither the 25 HP. or the Phantom require oil coolers, whereas with Peregrine and J.lll such a fitting appears to be necessary. Therefore we consider that the evidence at present is very definitely in favour of timing gears at the front end and a single flywheel bearing. Hs.{Lord Ernest Hives - Chair} | ||